eslint/docs/src/rules/no-restricted-globals.md

   1 ---
   2 title: no-restricted-globals
   3 layout: doc
   4 rule_type: suggestion
   5 related_rules:
   6 - no-restricted-properties
   7 - no-restricted-syntax
   8 ---
   9
  10
  11 Disallowing usage of specific global variables can be useful if you want to allow a set of global
  12 variables by enabling an environment, but still want to disallow some of those.
  13
  14 For instance, early Internet Explorer versions exposed the current DOM event as a global variable
  15 `event`, but using this variable has been considered as a bad practice for a long time. Restricting
  16 this will make sure this variable isn't used in browser code.
  17
  18 ## Rule Details
  19
  20 This rule allows you to specify global variable names that you don't want to use in your application.
  21
  22 ## Options
  23
  24 This rule takes a list of strings, where each string is a global to be restricted:
  25
  26 ```json
  27 {
  28     "rules": {
  29         "no-restricted-globals": ["error", "event", "fdescribe"]
  30     }
  31 }
  32 ```
  33
  34 Alternatively, the rule also accepts objects, where the global name and an optional custom message are specified:
  35
  36 ```json
  37 {
  38     "rules": {
  39         "no-restricted-globals": [
  40             "error",
  41             {
  42                 "name": "event",
  43                 "message": "Use local parameter instead."
  44             },
  45             {
  46                 "name": "fdescribe",
  47                 "message": "Do not commit fdescribe. Use describe instead."
  48             }
  49         ]
  50     }
  51 }
  52 ```
  53
  54 Examples of **incorrect** code for sample `"event", "fdescribe"` global variable names:
  55
  56 ::: incorrect
  57
  58 ```js
  59 /*global event, fdescribe*/
  60 /*eslint no-restricted-globals: ["error", "event", "fdescribe"]*/
  61
  62 function onClick() {
  63     console.log(event);
  64 }
  65
  66 fdescribe("foo", function() {
  67 });
  68 ```
  69
  70 :::
  71
  72 Examples of **correct** code for a sample `"event"` global variable name:
  73
  74 ::: correct
  75
  76 ```js
  77 /*global event*/
  78 /*eslint no-restricted-globals: ["error", "event"]*/
  79
  80 import event from "event-module";
  81 ```
  82
  83 :::
  84
  85 ::: correct
  86
  87 ```js
  88 /*global event*/
  89 /*eslint no-restricted-globals: ["error", "event"]*/
  90
  91 var event = 1;
  92 ```
  93
  94 :::
  95
  96 Examples of **incorrect** code for a sample `"event"` global variable name, along with a custom error message:
  97
  98 ::: incorrect
  99
 100 ```js
 101 /*global event*/
 102 /* eslint no-restricted-globals: ["error", { name: "event", message: "Use local parameter instead." }] */
 103
 104 function onClick() {
 105     console.log(event);    // Unexpected global variable 'event'. Use local parameter instead.
 106 }
 107 ```
 108
 109 :::